This invention relates to a composition containing organic dicarbonates and its use for soil disinfection and combating plant diseases.
The use of pyrocarbonic acid esters (organic dicarbonates) as preservatives for perishable materials is known from German Published Specification No. 1,011,709. However, the use of organic dicarbonates in plant protection did not appear possible, particularly because of their property - highly desirable in preserving foodstuffs - of reacting quantitatively and irreversibly, within a few hours, with compounds which contain active hydrogen atoms, and in the presence of water, to give physiologically harmless reaction products.
It has been disclosed to employ diethyl dicarbonate (DEDC) in greenhouses, before or after planting of seedlings, in order to disinfect the soil or disinfect the seed (Report 1969 of the Horticultural Research Institute of Ontario, pages 99 - 104).
However, in attempting to use diethyl dicarbonate for the disinfection of soil, it was found that in each case an undesirable and adverse change in the soil texture resulted, which can be described as a hardening or encrusting of the upper layer of the soil. In many cases, furthermore, only an inadequate or intermittent effect was found, which was attributable to a decomposition of the diethyl dicarbonate in the ethyl alcohol stock solution or in the aqueous watering solution prepared therefrom. This was because for the experiments, as described in the above-mentioned literature reference, page 100, diethyl dicarbonate was first dissolved in 95% strength ethyl alcohol and then suitably diluted with water. The decomposition of diethyl dicarbonate in alcoholic solution has already been known for a considerable time (compare Baycovin for the Cold Sterilisation of Beverages, pages 4 and 5, BAYER Company Leaflet, 1964).
Furthermore, it was found that the change in the soil texture is attributable to the alcohol content of the watering solution used.
Accordingly, a composition containing organic dicarbonates which does not contain any alcohol and in which the organic dicarbonate remains stable over a long period was sought. This is because, for practical use, it is essential that in particular the concentrate should retain its full activity over prolonged periods, since special storage measures require too much labour. Furthermore, it is necessary to ensure complete solution of the organic dicarbonate since the undiluted organic dicarbonates frequently cause plant damage.